This invention relates to a digital system for video display, and more particularly to a method and apparatus for digital video output processing to approximate the desirable smooth picture characteristics of an analog video output such as is generated by a TV camera or scan converter tube.
There are many reasons for using a digital system for video display. One is to provide a more versatile video scan converter than is possible with an analog scan converter tube. However, a digital video system does have its own problems. A primary problem is that the quantified picture elements (pixels) present a quantified or structured appearance of the display.
What is required in a digital system for video display is video output processing to transform the structured output to an output that emulates the gaussian characteristics of an analog output. The transformed digital output may then be displayed with the picture characteristic of an analog video system. An advantage is not only reduction of the quantization effects characteristic of a digital display system, but also a reduction of interfield flicker typical of digital display systems.
In the past, the digital output transformation has usually depended upon analog filtering to smooth the quantified pixels. A problem with that technique is that the smoothing occurs only along the horizontal axis. Also analog filters involve phase shifts and resultant rise time characteristics which do not match the desired gaussian function. In order to transform the digital video output to an output which emulates an analog video output, filtering would be required in both axes, and that simply would not be possible with just a filter to transform the digital video output into an analog video output.